B-52 Stratofortress Design
The basic configuration of the B-52 is similar in concept to that of the B-47. The shoulder location of the sweptback wing, wing-mounted engines, and bicycle landing gear are all reminiscent of the earlier aircraft. However, the B-52 is a much larger and heavier aircraft than its predecessor.
The wing of the B-52 has a sweepback angle at the quarter chord of 35°, an aspect ratio of 8.56, and airfoil thickness ratios that vary from 14 percent at the root to 8 percent at the tip (these thickness ratios are only approximate). Fowler-type single-slotted flaps for lift augmentation are located at the trailing edge of the wing. Hydraulically actuated spoilers are used for lateral control and, in the symmetrically deployed configuration, assist in flight-path control during landing approach and braking during rollout. On the A through F models of the aircraft, lateral control was provided by the spoilers working in conjunction with conventional ailerons. Wing area of the B-52 is 4000 square feet, nearly three times larger than that of the B-47.
Elevators and rudder, both of small chord, are used for longitudinal and directional control. An aerodynamic servotab system actuates these surfaces in response to the pilot's control inputs. A hydraulically adjustable stabilizer is used for trimming the aircraft longitudinally. This surface has sufficient aerodynamic power to rotate the aircraft on takeoff-, the B-47, which did not have an adjustable stabilizer, could not be rotated and was flown off the runway at the attitude angle imposed by the bicycle landing gear. The far forward position of the aircraft center of gravity relative to the rear bogie requires an aerodynamic moment for rotation much larger than could be provided by the small, manually actuated elevators.
The landing gear of the B-52 is of the same bicycle arrangement as employed on the B-47 but has four two-wheel bogies instead of the two bogies used on the earlier aircraft. As compared with their location on the B-47, the outrigger wheels are positioned much nearer the wingtip on the B-52. An interesting feature of the B-52 landing gear greatly eases the problems posed by crosswind landings. Both the front and rear bogies can be set at angles of as much as 20° to either side of the straight-ahead position. In a crosswind landing, consequently, the aircraft can be headed directly into the wind while rolling down a runway not aligned with the wind. Only the front bogies are used for steering on the ground. Although the wing spoilers obviate the need for an approach chute on the B-52, a 44-foot-diameter braking chute is provided for deployment in the landing rollout. The aircraft is not equipped with JATO units for use on takeoff.
As with so many successful aircraft, the term B-52 encompasses a whole family of generically related types of similar appearance but with major and minor differences in systems, equipment, and performance. All production models of the B-52 have been powered by eight engines located in pairs of two in four nacelles. All four of the nacelles are attached to the wings by sweptforward pylons that extend below the lower surface of the wing. Except for the B-52H, all models of the aircraft have been equipped with a version of the Pratt & Whitney J-57 turbojet engine of about 13 750 pounds thrust. A fan version of the J-57, the TF-33 of 17 000 pounds thrust, powers the B-52H. This engine is essentially similar to the Pratt & Whitney JT3D turbofan that powers the Boeing 707 and Douglas DC-8 commercial airliners. Much improved performance, particularly range and takeoff field length, resulted from application of the turbofan engine to the B-52.
As an indication of the capability of the B-52 with in-flight refueling, a nonstop flight of 24 325 miles was made around the world in January 1957. The flight required 45 hours and 19 minutes. The unrefueled range of the aircraft may be judged by the world-record nonstop flight of 12 532 miles made by a B-52H on January 10 and 11, 1962. Average speed for the flight was 575 miles per hour, and elapsed time was 22 hours and 9 minutes. This world-record flight certainly attests to the high maximum lift-drag ratio of the aircraft, the low specific fuel consumption of the engines, and the large fuel capacity of the aircraft that, in normal operations, can accommodate an astonishing 47 975 gallons of fuel. (An average American automobile could be driven 12 000 miles a year for about 80 years on this quantity of fuel.) Fuel tanks are located in both the wing and fuselage, and a 700-gallon external tank is carried under each wing.
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